# half life?

Discussion in 'Drug Testing' started by comfortably numb 010, Aug 23, 2006.

1. ### comfortably numb 010Registered

what do you mean when you say "the half-life of marijuana can be anywhere from 1-10 days in your system"

does that mean thats how long you can test positive? how long its in your system? i'm just kind of unsure. thanks a bunch

2. ### MetasteelRegistered+

Well, in chemistry and physics, the half life of an atom is the amount of time the atom takes to radioactively decompose by a half. i.e Two half lifes of an atom and the atom would be a quarter it's original size. So I guess it means how long it taks half the THC to work out of your system.

3. ### dfguyRegistered+

And for me It's alot longer, I took a test, GC/MS on July 29, it came back at 44 ng/mL. Took another test, GS/MS on Aug. 18, 20 days later and It came back at 20 ng/mL. So the Half-Life in me is about twice as long.
Now I know everyone is different, I'm in my 40s, 5'10 160. and have been painting my house, not like I sit around all day. I was smoking a lot of top dollar week, about a gram a day for years. I was able to pass a home test after 19 days. My test on the 18th. was after 58 days. At this rate it will be another two months before I'm at Zero ng/mL

4. ### dfguyRegistered+

What I have read it means how long it takes leaves your system, The cut off for a drug "screen", like a home test or what they do for employment it's "on-site", it's a dip test. Is 50 ng/ml. If it's positive it goes to a lab where they do a GC/MS and it run thru some kind of machine It's much more accurate and expensive, it's cut off is 15 or 10 ng/mL depenting on the Lab.

So back to the Half-live, Lets say you were at 100 ng/mL on Aug. 1, and the half-life for you is 10 days, on Aug. 10th. you would be at 50 ng/mL, might fail a drug "screen", on Aug 20th, you would be at 25 ng/mL , you would pass a "screen" , but fail a "test" (GC/MS). On Aug. 30th. you would be at 12.5 ng/mL, 10 days later 6.25 ng/mL, 10 more 3.12, and so on and so on. Yours might be less, or Like me, longer.

5. ### FakeBoobsRuleSmackdown Moderation

Exactly Dfguy, great example. The technical definition would be the time required for half the amount of a substance (as a drug or radioactive tracer) in or introduced into a living system or ecosystem to be eliminated or disintegrated by natural processes. So for every half life completed, half of the THC will be eliminated. In Dfguy's example, that doesn't mean that on August 9 you would still be at the level you were on August 1 and suddenly on August 10 it makes this huge drop off. It is constantly eliminated but the measuring milestones are measured in half-lifes. Even though this link and graph represent radioactive half-life, the graph would be the same for THC.

http://www.lbl.gov/abc/experiments/Experiment6.html

The point 1 on the left side of the graph would represent the time when you last consumed THC and the graph would be accurate unless more THC were introduced to your system. Disregard the numbers on the bottom of the graph as these numbers would represent the half life of THC. Unfortunately, these numbers vary greatly from person to person. The increments could be as small 20 hours (then 40 hours, 60 hours, 80 hours, 100 hours etc) or as long as 10 days (then 20 days, then 30 days, then 40 days etc.).

Last edited: Aug 24, 2006